(a) Field of the Invention
The present invention relates to an improved, prefabricated culvert unit of the type comprising a prefabricated bottom plate, a pair of prefabricated sidewall plates that may be assembled onto the bottom plate, and a prefabricated cover plate that may be assembled on top of the sidewall plates to form altogether a closed duct.
(b) Brief Description of the Prior Art
A prefabricated culvert unit of the above mentioned type is disclosed in Applicant's Korean utility model application No. 85-18268. The culvert unit disclosed in this application has numerous advantages but it also has some disadvantages.
First of all, in this Applicant's prior system, the cover plate is merely laid on top of the upper edges of the sidewall plates. As a result, it is easily subject to inadvertant shifting and misalignment, especially when the culvert is being embedded into the ground.
Another disadvantage of the Applicant's prior culvert unit is that its sidewall plates are both provided at their lower edges with integral projection that extend laterally outwardly and are of such a length that they extend well beyond the side edges of the bottom plate.
A further disadvantage of the Applicant's prior unit is that the bottom panel which is arc-shaped has side edges which are too thin and sharp to bear some of the pressures that may be applied over them during transportation or building on the premises.